1. Field of the Invention
The present invention relates to an aqueous dispersion for electrodeposition, a high dielectric constant film formed from the aqueous dispersion and electronic parts provided with the high dielectric constant film.
2. Description of the Prior Art
A technique is known whereby a high dielectric constant layer is formed on a multilayer printed wiring board or the like and the layer is utilized as a condenser. The high dielectric constant layer is fabricated, for example, by a method in which a solution of a thermosetting resin in an organic solvent also containing an added high dielectric constant inorganic powder is impregnated into afiber-reinforcement such as glass fibers to compensate for the fragility of the thermosetting resin, and the solvent is then scattered and allowed to harden.
Because this prior art method uses a fiber-reinforcement it is not possible to achieve significant reduction in the thickness of the high dielectric constant layer (for example, to under 50 xcexcm), and since the dielectric constant of a fiber-reinforcement is lower than that of an inorganic powder such as TiO2, it has not been possible to obtain condensers with high capacitance.
In order to solve this problem, Japanese Laid-open Patent Publication No. 12742 of 1997 discloses a high dielectric constant film that eliminates the need for the fiber-reinforcement in the aforementioned construction by using a thermosetting resin with film forming properties. According to this publication, a resin varnish is prepared containing the thermosetting resin and high dielectric constant inorganic powder, and this is coated and dried to produce a film.
However, since high dielectric constant inorganic powders usually have a high specific gravity and thus settle in resin varnishes with time, causing a lack of shelf life for such resin varnishes, it has been necessary to prepare a fresh resin varnish just before production of the film. Because the film is formed by coating and drying the solution, it is difficult to achieve a high film thickness precision for the obtained film, and the manageability has not been very good for formation of films on only specific locations of boards.
In addition, when forming a high dielectric constant layer selectively on a desired wiring, it has been necessary to prescribe the location of formation by a combination of photolithography and printing methods for conventional resin varnishes. However, formation methods using photolithography are associated with problems of high cost and complicated steps, while printing methods are associated with the problem of poor working precision.
It is an object of the present invention to provide an aqueous dispersion for electrodeposition which has excellent shelf life and can form thin, high dielectric constant films by electrodeposition, as well as a high dielectric constant film formed from the aqueous dispersion and electronic parts provided with the high dielectric constant film.
The present inventors have completed the present invention upon finding that the aforementioned problems can be overcome by using an aqueous dispersion for electrodeposition that comprises electrodepositable organic particles and small-sized inorganic particles dispersed in an aqueous medium.
That is, the aqueous dispersion for electrodeposition according to the first aspect of the invention is characterized by comprising inorganic particles with a mean particle size of no greater than 1 xcexcm and a dielectric constant of at least 30, and organic particles composed of either or both a polymerizable compound and a polymer, dispersed in an aqueous medium. The aqueous dispersion is preferably used for electrodeposition to give a film with a dielectric constant of 6 or greater. The inorganic particles are preferably composed of a titanium-based metal oxide, and the organic particles are preferably charged on the particle surfaces and are composed of a polyimide-based resin. The volume ratio of the inorganic particles and organic particles is preferably in the range of 5/95-80/20.
The high dielectric constant film according to the second aspect of the invention is characterized by being formed by electrodeposition using the aqueous dispersion for electrodeposition according to the first aspect.
The electronic part according to the third aspect of the invention is characterized by being provided with a high dielectric constant film according to the second aspect.
The aqueous dispersion for electrodeposition of the invention has excellent shelf life as explained above, and hence it is not necessary to prepare the solution for each high dielectric constant film fabrication. The aqueous dispersion of the invention can therefore enhance productivity for high dielectric constant films. Furthermore, since an aqueous medium is used unlike the varnish, an advantage is also provided in terms of the working environment. Since the high dielectric constant film of the invention is formed by electrodeposition using the aforementioned aqueous dispersion, the film thickness control is facilitated through adjustment of the electrodeposition conditions, while the film formability and follow-up properties to the substrate are superior to cases where the film is formed by application. It is also possible to form the high dielectric constant film selectively on a conductive substrate (wiring and the like), and to produce highly precise high dielectric constant films more inexpensively than by photolithography or printing methods. The high dielectric constant film of the invention has both low thickness and high dielectric constant, and can therefore be suitably used for such electronic parts as printed circuit boards, semiconductor packages, condensers and high-frequency antennas. Electronic parts of the invention provided with the aforementioned high dielectric constant film can be produced in miniature and thin-film form.
The present invention will now be explained in further detail.
The dielectric constant of the inorganic particles used for the invention is 30 or greater, preferably 50 or greater and most preferably 70 or greater. The inorganic particles used are preferably composed of a metal oxide, and titanium-based metal oxides are particularly preferred. Here, xe2x80x9ctitanium-based metal oxidesxe2x80x9d means compounds including titanium element and oxygen element as essential elements. Specifically there may be mentioned metal oxides based on titanium dioxide, barium titanate, lead titanate, strontium titanate, bismuth titanate, magnesium titanate, neodymium titanate, calcium titanate and the like. Metal oxides based on xe2x80x9ctitanium dioxidexe2x80x9d include titanium dioxide alone, as well as systems of titanium dioxide also containing small amounts of other added compounds, and they maintain the crystal structure of the major component of titanium dioxide; these conditions also apply to metal oxides of other systems. According to the invention, it is particularly preferred to use inorganic particles composed of titanium dioxide-based (rutile structure) or barium titanate-based metal oxides. For improved dispersability in aqueous media, particles composed of these materials having the particle surfaces modified with silica, alumina or the like are suitable for use.
The mean particle size of the inorganic particles must be no greater than 1 xcexcm, preferably no greater than 0.5 xcexcm and more preferably no greater than 0.2 xcexcm. If the mean particle size exceeds 1 xcexcm, the dispersability of the inorganic particles in aqueous media will be insufficient, making it impossible to achieve sufficient shelf life. There is no particular restriction for the minimum mean particle size, but it is normally 0.02 xcexcm or greater.
(2-1) Composition of Organic Particles
The organic particles used for the invention are composed of xe2x80x9ceither or both a polymerizable compound and a polymerxe2x80x9d. Here, xe2x80x9cpolymerizable compoundxe2x80x9d refers to a compound with a polymerizable group, and its meaning includes precursor polymers that have not been fully cured, polymerizable oligomers, monomers and the like. xe2x80x9cPolymerxe2x80x9d refers to a compound that has undergone substantially complete polymerization reaction. However, the polymer may also be crosslinked after electrodeposition, by heating, moisture or the like. The surfaces of the organic particles are preferably charged to allow electrodeposition. The surface charge may be anionic or cationic, but is preferably cationic in order to prevent electrode oxidation during the electrodeposition.
The organic particles are preferably composed of one, two or more types selected from among polyimide-based resins, epoxy-based resins, acrylic-based resins, polyester-based resins, fluorine-based resins and silicone-based resins. They may also contain other components in addition to these resins. The resins may also be chemically bonded each other or to other components.
According to the invention it is possible to form a high dielectric constant film with excellent mechanical properties, chemical properties and electrical properties by electrodeposition, and therefore it is particularly preferred to use organic particles composed mainly of a polyimide-based resin. xe2x80x9cPolyimide-based resinxe2x80x9d means a precursor polymer (such as polyamic acid and the like) that can be cured by heating or the like after electrodeposition, a monomer that can be used to form a polyimide-based resin, or an oligomer or the like, and this applies to the other resins as well. The xe2x80x9cpolyimide-based resinxe2x80x9d also includes polyimide resins or their precursors, copolymer resins or precursor polymers of monomers that can be used to form polyimide resins and other monomers, and reaction products of polyimide resins or their precursors with other compounds; this also applies to the other resins.
(2-2) Aqueous Emulsion of Organic Particles
The aqueous dispersion of the invention is normally prepared using an aqueous emulsion wherein the organic particles are dispersed in an aqueous medium. The water content of the aqueous medium is usually at least 5 wt %, preferably at least 10 wt %, more preferably 20-98 wt % and most preferably 30-95 wt %. As other media that may be used with water depending on the case there may be mentioned aprotic polar solvents used for the production of polyamic acids or polyimides, as well as esters, ketones, phenols, alcohols and the like.
The following explanation will concern a method for production of an aqueous emulsion of organic particles composed mainly of a polyimide-based resin (hereunder referred to as xe2x80x9cpolyimide-based resin emulsionxe2x80x9d), an aqueous emulsion of particles composed mainly of an epoxy-based resin (hereunder, xe2x80x9cepoxy-based resin emulsionxe2x80x9d), an aqueous emulsion of particles composed mainly of an acrylic-based resin (hereunder, xe2x80x9cacrylic-based resin emulsionxe2x80x9d), an aqueous emulsion of particles composed mainly of a polyester-based resin (hereunder, xe2x80x9cpolyester-based resin emulsionxe2x80x9d), an aqueous emulsion of particles composed mainly of a fluorine-based resin (hereunder, xe2x80x9cfluorine-based resin emulsionxe2x80x9d) and an aqueous emulsion of particles composed mainly of a silicone-based resin (hereunder, xe2x80x9csilicone-based resin emulsionxe2x80x9d).
(2-2-i) Method for Production of Polyimide-based Resin Emulsion
The organic particles of the invention are preferably composed of a polyimide-based resin to allow formation of a polyimide-based high dielectric constant film with excellent mechanical properties, chemical properties and electrical properties. As preferred methods for fabrication of a polyimide-based film by electrodeposition there may be mentioned the following two methods.
[1] A method in which a polyimide-based resin emulsion comprising composite particles of (A) an organic solvent-soluble polyimide and (B) a hydrophilic polymer is used as the electrodeposition solution for electrodeposition of the composite particles.
[2] A method in which a polyimide-based resin emulsion comprising particles including composite particles of (C) a polyamic acid and (D) a hydrophobic compound is used as the electrodeposition solution for electrodeposition of the particles, and the electrodeposited polyamic acid is heated for dehydration ring closure.
As methods for production of the polyimide-based resin emulsion used for this method, there may be mentioned the method described in Japanese Laid-open Patent Publication No. 49951 of 1999 for method [1], and the method described in Japanese Laid-open Patent Publication No. 60947 of 1999 for method [2].
The method for production of the polyimide-based resin emulsion to be used in method [1] will now be explained in greater detail.
The method for synthesis of the xe2x80x9c(A) organic solvent-soluble polyimidexe2x80x9d is not particularly restricted, and for example, the polyimide may be synthesized by mixing a tetracarboxylic dianhydride and a diamine compound in an organic polar solvent for polycondensation to obtain a polyamic acid, and then subjecting the polyamic acid to heating imidation or chemical imidation to promote a dehydrating ring closure reaction. Alternatively, polycondensation of the tetracarboxylic dianhydride and the diamine compound may be carried out in multiple stages to synthesize a polyimide with a block structure.
The organic solvent-soluble polyimide is preferably one with at least one type of reactive group (a) such as a carboxyl group, amino group, hydroxyl group, sulfonic acid group, amido group, epoxy group or isocyanate group. As a method for synthesis of the polyimide with the reactive group (a) there may be mentioned, for example, a method whereby a carboxylic acid dianhydride, diamine compound, carboxyl acid monoanhydride, monoamine compound or the like which has the reactive group (a) is used for synthesis of the polyamic acid, and the reactive group (a) is left after the dehydration ring closure reaction.
The xe2x80x9c(B) hydrophilic polymerxe2x80x9d comprises a hydrophilic polymer having at least one from among amino groups, carboxyl groups, hydroxyl groups, sulfonic acid groups, amido groups and the like, as the hydrophilic group, and having a solubility in water at 20xc2x0 C. of normally 0.01 g/100 g or greater, and preferably 0.05 g/100 g or greater. In addition to the hydrophilic group, it also preferably has one or more reactive groups (b) that can react with the reactive group (a) in component (A). As examples of such reactive groups (b) there may be mentioned epoxy groups, isocyanate groups and carboxyl groups, as well as the same hydrophilic groups mentioned above. This type of hydrophilic polymer may be obtained either by homopolymerization or copolymerization of monovinyl monomers having the hydrophilic group and/or the reactive group (b), or by copolymerization of such monovinyl monomers with other monomers.
The (A) organic solvent-soluble polyimide and the (B) hydrophilic polymer are selected so that the reactive group (a) and the reactive group (b) in the hydrophilic polymer are combined with the appropriate reactivity and the polyimide and hydrophilic polymer are, for example, mixed in a dissolved state in an organic solvent for reaction, with heating if necessary, after which the reaction solution is combined with an aqueous medium with optional removal of at least a portion of the organic solvent, to obtain a polyimide-based resin emulsion comprising composite particles wherein the polyimide and the hydrophilic polymer are bonded together in the same particles.
The method for production of the polyimide-based resin emulsion using the method of [2] above will now be explained in fuller detail.
The method of synthesizing the xe2x80x9c(C) polyamic acidxe2x80x9d as the polyimide precursor is not particularly restricted, and for example, the polyamic acid may be obtained by polycondensation reaction of a tetracarboxylic dianhydride and diamine compound in an organic polar solvent. Alternatively, polycondensation reaction of the tetracarboxylic dianhydride and the diamine compound may be carried out in multiple stages to synthesize a polyamic acid with a block structure. A polyamic acid that is partially imidated by dehydration ring closure of the polyamic acid may also be used.
The xe2x80x9c(D) hydrophobic compoundxe2x80x9d is a compound with a group that can react with at least the amic acid group of the polyamic acid (hereunder referred to as xe2x80x9creactive groupxe2x80x9d). As examples for the reactive group there may be mentioned epoxy, isocyanate, carbodiimide, hydroxyl, mercapto, halogen, alkylsulfonyl, arylsulfonyl, diazo and carbonyl groups. One or more of these reactive groups may be present in the hydrophobic compound. xe2x80x9cHydrophobicxe2x80x9d means that its solubility in water at 20xc2x0 C. is normally less than 0.05 g/100 g, preferably less than 0.01 g/100 g, and more preferably less than 0.005 g/100 g.
As examples of such hydrophobic compounds there may be used one or more types selected from among epoxified polybutadiene, bisphenol A-based epoxy resins, naphthalene-based epoxy resins, fluorene-based epoxy resins, biphenyl epoxy resins, glycidyl ester epoxy resins, acryl glycidyl ether, glycidyl (meth)acrylate, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N,N,Nxe2x80x2,Nxe2x80x2-tetraglycidyl-m-xylenediamine, tolylene diisocyanate, dicyclohexyl carbodiimide, polycarbodiimide, cholesterol, benzyl alcohol, p-toluenesulfonic acid esters, ethyl chloroacetate, triazinetrithiol, diazomethane, diacetone (meth)acrylamide and the like.
The (C) polyamic acid and (D) hydrophobic compound are, for example, mixed in a dissolved state in an organic solvent, after which the reaction solution is combined with an aqueous medium with optional removal of at least a portion of the organic solvent, to obtain a polyimide-based resin emulsion comprising composite particles containing the polyamic acid and the hydrophobic compound in the same particles.
The tetracarboxylic dianhydride used for the method of [1] and [2] above is not particularly restricted, and as examples there may be mentioned aliphatic tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides such as butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 3,3xe2x80x2,4,4xe2x80x2-dicyclohexyltetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride and 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]-furan-1,3-dione;
aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3xe2x80x24,4xe2x80x2-benzophenonetetracarboxylic dianhydride and 3,3xe2x80x2,4,4xe2x80x2-biphenylsulfonetetracarboxylic dianhydride; and the like. These tetracarboxylic dianhydrides may be used alone or in combinations of two or more.
The diamine compound used for the method of [1] or [2] above is not particularly restricted, and as examples there may be mentioned aromatic diamines such as p-phenylenediamine, 4,4xe2x80x2-diaminodiphenylmethane and 2,2-bis[4-(4-aminophenoxy)phenyl]propane;
aliphatic diamines and alicyclic diamines such as 1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine and 4,4xe2x80x2-methylenebis(cyclohexylamine);
diamines with two primary amino groups and a nitrogen atom other than that of the primary amino groups in the molecule, such as 2,3-diaminopyridine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, 2,4-diamino-5-phenylthiazole and bis(4-aminophenyl)phenylamine;
mono-substituted phenylenediamines; and
diaminoorganosiloxanes. These diamine compounds may be used alone or in combinations of two or more.
(2-2-ii) Method for Production of Epoxy-based Resin Emulsion
The method for production of an epoxy-based resin emulsion is not particularly restricted, and any conventional publicly known method may be used such as the method described in Japanese Laid open Patent Publication No. 235495 of 1997 or No. 208865 of 1997, for example.
(2-2-iii) Method for Production of Acrylic-based Resin Emulsion
The method for production of an acrylic-based resin emulsion is not particularly restricted, and for example, it may be produced by a common emulsion polymerization method. As the monomers there may be used one, two or more types selected from among common acrylic-based and/or methacrylic-based monomers. Here, the particles are preferably rendered electrodepositable by copolymerization with a monomer with a cationic group such as an amino, amido or phosphono group or a monomer with an anionic group such as a carboxyl or sulfonic acid group, and the copolymerization degree is preferably 5-80 wt % (more preferably 10-50 wt %) with respect to the total monomer used. As specific examples of monomers with such amino groups there are preferably used dimethylaminoethyl acrylate and dimethylamino propylacrylamide.
(2-2-iv) Method for Production of Polyester-based Resin Emulsion
The method for production of a polyester-based resin emulsion is not particularly restricted, and any conventional publicly known method may be used such as the method described in Japanese Laid-open Patent Publication No. 10663 of 1982, No. 70153 of 1982 or No. 174421 of 1983, for example.
(2-2-v) Method for Production of Fluorine-based Resin Emulsion
The method for production of a fluorine-based resin emulsion is not particularly restricted, and any conventional publicly known method may be used such as the method described in Japanese Laid-open Patent Publication No. 268163 of 1995, for example.
(2-2-vi) Method for Production of Silicone-based Resin Emulsion
The method for production of a silicone-based resin emulsion is not particularly restricted, and any conventional publicly known method may be used such as the method described in Japanese Laid-open Patent Publication No. 60280 of 1998.
The aqueous dispersion of the invention is one in which the aforementioned organic particles and inorganic particles are dispersed in an aqueous medium. The meaning of xe2x80x9caqueous mediumxe2x80x9d is the same as given above.
The volume ratio of the inorganic particles and organic particles in the aqueous dispersion is preferably in the range of 5/95-80/20, and more preferably 10/90-60/40. When the inorganic particle proportion is less than 5 vol %, it becomes difficult to obtain a high dielectric constant film. On the other hand, when the proportion of inorganic particles exceeds 80 vol %, the film forming properties of the film are undesirably inadequate.
The pH of the aqueous dispersion is preferably 2-10 (more preferably 3-9), the solid content is preferably 1-50 wt % (more preferably5-20 wt %), and the viscosity at 20xc2x0 C. is preferably 1-100 mPaxc2x7s. If the pH, solid content or viscosity fall outside of these specified ranges, the dispersability of the particles is reduced leading to a lack of shelf life, and the manageability during handling and use is often impaired.
The aqueous dispersion may be prepared by a method whereby [1] an aqueous dispersion of the inorganic particles is mixed with an aqueous dispersion of the organic particles, or [2] the inorganic particles are added to and mixed with an aqueous dispersion of the organic particles. Method [1] is preferred. The pH of the aqueous dispersion of the inorganic particles before its mixture with the aqueous dispersion of the organic particles is preferably adjusted to pH 2-10 using nitric acid, sulfuric acid, potassium hydroxide or the like in order to improve the stability during mixing.
The aqueous dispersion of the invention may have a shelf life which allows storage for a period of 5 days or longer (preferably 7 days or longer, more preferably 10 days or longer, and especially 14 days or longer) at 20xc2x0 C., without causing bilayer separation or notable changes in viscosity.
The aqueous dispersion of the invention may also contain, in addition to the aforementioned organic particles and inorganic particles, also at least one selected from among organosilanes represented by the following formula (1), hydrolysates in which a portion or all of the hydrolyzable groups of the organosilane have been hydrolyzed, and partial condensates in which the hydrolysate has been partially dehydrated and condensed (hereunder referred to as xe2x80x9corganosilane condensate and the likexe2x80x9d). The film formed from the aqueous dispersion for electrodeposition has excellent mechanical properties, chemical properties, hardness and electrical properties due to crosslinking of the organosilane condensates and the like in the film, particularly when heat curing is carried out after electrodeposition.
(R1)nSi(OR2)4xe2x88x92nxe2x80x83xe2x80x83(1)
where R1 represents a hydrogen atom or a monovalent organic group of 1-8 carbons, R2 represents an alkyl group of 1-5 carbons, an acyl group of 1-6 carbons or a phenyl group, and n is an integer of 1 or 2. R1 and R2 may be the same or different.
As organic groups of 1-8 carbons for R1 in formula (1) there may be mentioned linear or branched alkyl groups, halogen-substituted alkyl groups, vinyl groups, phenyl groups and 3,4-epoxycyclohexylethyl groups. R1 may also have a carbonyl group. R1 is preferably an alkyl group of 1-4 carbons or a phenyl group.
As alkyl groups of 1-5 carbons or acyl groups of 1-6 carbons for R2 there may be mentioned methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, acetyl, propionyl and butyryl. R2 is preferably an alkyl group of 1-4 carbons.
As examples of preferably used organosilanes there may be mentioned dimethyldimethoxysilane, dimethyldiethoxysilane, isobutyltrimethoxysilane and phenyltriethoxysilane. These organosilanes may be used alone or in combinations of two or more.
The xe2x80x9corganosilane condensate and the likexe2x80x9d preferably form composite-style particles with organic particles in the aqueous dispersion for electrodeposition according to the invention. For the xe2x80x9ccomposite-style particlesxe2x80x9d, the compound composing the organic particles and the organosilane condensate and the like are chemically bonded, or the organosilane condensate and the like is adhered to the surface or inside of the organic particles.
The organosilane condensate and the like is used in an amount of preferably 0.1-500 parts by weight and more preferably 0.5-250 parts by weight to 100 parts by weight of the organic particles. If the organosilane condensate and the like is used at less than 0.1 part by weight it may not be possible to achieve the desired effect, while if it is used at greater than 500 parts by weight the film will tend to have lower adherence.
The composite-style particles may be produced by either of the following methods [1] or [2]. The methods may also be used in combination.
[1] The organosilane is added to the organic particle emulsion for absorption of at least a portion of the organosilane into the organic particles, followed by progressive hydrolysis reaction and condensation reaction of the organosilane.
[2] A reaction is conducted in which the organic particles are produced in the presence of the organosilane condensate and the like dispersed in the aqueous medium.
For absorption of the organosilane into the organic particles by method [1], the organosilane may be added to the emulsion and adequately stirred. At this stage, at least 10 wt % (more preferably at least 30 wt %) of the added organosilane is absorbed into the particles. In order to avoid progression of the hydrolysis/condensation reaction of the organosilane before absorption has sufficiently been accomplished, the pH of the reaction system may be adjusted to normally 4-10, preferably 5-10 and more preferably 6-8. The treatment temperature for absorption of the organosilane into the organic particles is preferably 70xc2x0 C. or below, more preferably 50xc2x0 C. or below and even more preferably 0-30xc2x0 C. The treatment time is normally 5-180 minutes, with about 20-60 minutes being preferred.
The temperature for the hydrolysis/condensation of the absorbed organosilane is normally 30xc2x0 C. or above, preferably 50-100xc2x0 C. and more preferably 70-90xc2x0 C., with the preferred polymerization time being 0.3-15 hours, and more preferably 1-8 hours.
For method [2], the organosilane is mixed in an aqueous solution of a strongly acidic emulsifying agent such as an alkylbenzenesulfonic acid using a homomixer or an ultrasonic mixer, and then subjected to hydrolysis/condensation to obtain an organosilane condensate and the like dispersed in the aqueous medium. The aforementioned organic particles are produced preferably by emulsion polymerization in the presence of the organosilane condensate and the like.
The aqueous dispersion of the invention may be used directly or it may be diluted or concentrated, with addition of appropriate publicly known additives if necessary, used as an electrodeposition solution for formation of a high dielectric constant film. A common electrodeposition method using the electrodeposition solution may be employed for electrodeposition of the inorganic particles and organic particles in the aqueous dispersion onto an electrode surface or the like, to produce a high dielectric constant film.
For production of a high dielectric constant film according to the invention, the resin components of the electrodeposited particles are preferably heat cured. The heat curing conditions are not particularly restricted, but the heating temperature is preferably 100-400xc2x0 C. and more preferably 150-300xc2x0 C. The heating time is preferably 5 minutes or longer, and more preferably 10 minutes or longer.
An aqueous dispersion according to the invention can give a high dielectric constant film with a dielectric constant of 6 or greater (more preferably 7 or greater). It can exhibit a volume resistivity of 1012 xcexa9xc2x7cm or greater (preferably 1013 xcexa9xc2x7cm or greater). The thickness of the high dielectric constant film is preferably no greater than 50 xcexcm (more preferably no greater than 30 xcexcm). The lower limit for the film thickness is not particularly restricted, but normally it is at least 1 xcexcm.
A high dielectric constant film according to the invention can be used to form thin, high capacitance condensers. Electronic parts such as printed circuit boards, semiconductor packages, condensers and high-frequency antennas provided with such high dielectric constant films can be built to small sizes and high integration.